DRAT - Doubly
Rotated AT Cut Crystals
DRAT is an acronym for Doubly Rotated AT. A DRAT is a crystal whose
frequency vs. temperature characteristic is determined by
controlling the angle of cut about two crystallographic axes in lieu
of just one axis.

DRATS include SC, IT and FC cut crystals. For a given frequency and
mode a DRAT has more mass that an AT Cut resonator making it less
susceptible to the frequency altering effects of gravity,
acceleration, vibrating, contamination, and shock. DRATs also
exhibit lower phase noise that AT Cut resonators.

The upper turn or inversion point for a DRAT is typically between
+65 deg. C and 95 deg. C and the frequency vs. temperature deviation
in that range is minimal. DRATs provide superior performance over AT
Cut resonators in terms of resistance to mechanical forces, absolute
frequency stability, phase noise and aging. Applications include
very high precision timing references, typically oven controlled
crystal oscillators OCXO.